Flat panel displays using liquid crystal display (LCD) technology are widely known and have found application in a number of fields for displaying visual information. In a flat panel LCD, the screen area, which is substantially rectangular, is divided into a large number of individual color dots. Each set of color dots is capable of displaying a full color gamut. It is known for the sets to comprise a three-dot combination of red, green and blue, a four-dot combination of red, green, green and blue, a four-dot combination of red, green, blue and white, and a six-dot combination of red, green, blue, yellow, cyan and magenta, as well as other combinations that allow a full color display. In an active matrix flat panel LCD, each color dot contains a transistor switch. A liquid crystal fluid, contained between a front plate and a rear plate, is twisted by a voltage which changes the axis of polarization of light, allowing the individual color dots to transmit or block light passing from a backlight source through the individual color filters. The color dots are arranged in a grid comprising rows and columns, and there can be several hundred or thousand vertical columns of color dots going across the display as well as hundreds or thousands of horizontal rows of color dots, resulting in most cases in more than 1,000,000 individual color dots. Each color dot has a vertical column and horizontal row grid address and is driven by electrical impulses fed along its respective row from a bus located on one of the side edges of the flat panel LCD and along its respective column from a top or bottom edge of the flat panel LCD. In general, the horizontal row drivers are referred to as gate drivers and the vertical column drivers are referred to as source drivers, but these may be reversed in practice, as will be known to those of skill in this art. In either case, the source driver signal provides the gray scale data for a given color dot, while the gate driver signal changes a given line of thin film transistors (“TFTs”) from “off” to “on” for a given “line time. ” This signal from the gate driver thereby allows the charging of a capacitor associated with the individual color dot, determining the voltage held by the color dot for an entire frame period.
In some critical applications, especially in vehicle applications where the overall display area is limited but it is desired to maximize image area while providing a degree of redundancy, the display area should be divided into at least one pair of side by side display areas, while retaining the visual impression of a single panel. However, since color dots near a junction line between the two adjacent display areas receive their respective signals from opposite sides of the display, these signals are vulnerable to a mismatch of their photometrics. If this is not corrected, a visually perceptible seam will occur along that junction line.
The very nature of a display panel dictates that a central portion of the panel contains the most critical information for the user. For example, critical electronic flight indicators such as the horizontal situation indicator (HSI), the attitude direction indicator (ADI), the altimeter and the air speed indicator will be located centrally on the panel, to be readily accessible to a pilot. In a large display panel, especially one that has a significantly large number of columns of color dots, as an “all glass” cockpit would have, it is desirable to drive side by side displays that define the overall panel display. However, this can place the distraction of a visually perceptible centerline or seam at the point of focus for the user.
Although this need has been initially described with reference to electronic flight indicator applications of flat panel LCDs, the need extends to a variety of other flat panel LCD applications, and the present invention is applicable to these other applications.
It is, therefore, an unmet objective of the prior art to mate a pair of side by side display areas on a single flat panel LCD, such that there is no visibly perceptible seam line along a junction line between the side by side display areas.